This application is in response to PA-06-478, Research on Rural Mental Health and Drug Abuse Disorders. One of the research areas highlighted by this PA is the examination of rural HIV transmission using social network analysis. The overall goal of the study is to examine the prevalence, incidence, and risk factors for HIV and other blood borne infections (BBIs) such as hepatitis B (HBV) and C (HCV) among rural Appalachian drug users using social network analysis and multilevel modeling. HIV continues to be a major public health problem in the United States, especially among drug users. However, little is known about HIV in rural areas in which there are marked health disparities. Therefore, given that studies among urban drug users have found that social network indicators are robust predictors of HIV risk, both social network and individual characteristics will be measured for their association with HIV risk among rural drug users. The specific aims are: 1) To determine the prevalence and incidence of HIV, HCV and HBV among rural injection and non- injection drug users; 2) To examine HIV and other BBI risk among rural injection and non-injection drug users; and 3) To examine longitudinal changes in rural HIV, HCV and HBV risk at 6-months, 12-months and 18- months post-baseline. To meet these aims, a sample 500 rural injection and non-injection drug users will be recruited using respondent driven sampling (RDS). In addition to biologic testing for HIV, HCV and HBV, rural participants will be given an interviewer-administered questionnaire pertaining to their social networks (drug, sexual and support networks), sociodemographics, drug use, HIV risk behaviors, psychiatric diagnoses, intravention and norms. Since individuals will be nested within networks, data will be analyzed using multilevel random effects regression that allows for the simultaneous examination of social network and individual-level risk. Consistent with the priorities of the NIDA AIDS Research Program, this proposal will explore the social network structure in a rural drug using population in order to better understand how network factors may affect HIV risk in rural areas using an innovative multilevel approach. Results from the proposed study will inform the design and implementation of HIV interventions in rural areas and help to determine the appropriate population for which to target such activities in order to reduce the morbidity and mortality associated with HIV and other BBIs. Although HIV remains a significant public health problem in the United States, especially among drug users, little is known about HIV risk in rural areas such as Appalachia. It has been shown in urban populations that relationships among drug users, also known as social networks, are important predictors of HIV risk. Therefore, this study seeks to characterize rural HIV risk by measuring both social network and individual behaviors in order to inform prevention activities in health resource-deprived rural areas.